[Đại số 7] Cần gấp

D

demon311

Đặt $x^2=\overline{207ab}$
Ta có: $20449 <20700 \le \overline{207ab} \le 20799 < 21025$
\Leftrightarrow $143^2<x^2<145^2$
\Rightarrow $x=144$
Vây\Rightarrow $\overline{207ab}=144^2=20736$
Vậy $\overline{ab}=36$
 
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